Chironomus apicatus Johannsen 1932

as variety of C. costatus Johannsen

Adult

Original description by Johannsen 1932

Male and female.    Differs from the typical form [i.e. C. costatus] in having the fore basitarsus 1.85 times tibia in length, the tarsi largely brown, only the two apical segments somewhat paler brown.  The mesonotal vittae are brownish.  Crossvein of wings brown.  Hypopygium as figured [below].  Length 5 mm.  Bred from larvae found in pools.

Illustration of the hypopygium of C. apicatus
From Johannsen (1932)

Karunakaran 1969 adds that the vittae of Singapore male specimens are pale orange yellow and that the abdominal tergites II-IV have small circular patches compared to prominent oval patches in C. costatus.  However, her material is most likely C. flaviplumus.
Additional data on anterior tarsi of type (thanks to Duncan Sivell, Natural History Museum, London):  Ta1 twice the length of Ta2; Ta2-4 subequal, but decreasing in length; Ta5 less than half the length of Ta4.

Larva: A small plumosus-type, length about 9.0 - 10.5 mm (males).  Lateral projections about 170 - 240 µm, posterior pair of ventral tubules usually longer (ant. 0.83 - 1.04 mm; post. 0.90 - 1.08 mm).  Anal tubules long with a constriction near centre.
Gular region pale to slightly darkened, frontoclypeus very slightly dark to dark.
Mentum with generally sharp teeth, c2 teeth well separated (type II), 4th laterals hardly reduced (type I-II).
About 13 - 15 teeth in pecten epipharyngis.  Premandible with inner tooth only about 1/3 wider than outer tooth, and about equal in length.
3rd inner tooth of mandible almost completely separated (type IIIB).

Cytology:  Four polytene chromosomes, probably with the pseudothummi-cytocomplex combination BF, CD, AE, G.  Possibly no nucleolus in arm G.


Arm G of C. apicatus

Breeding in pools.

Found: Type locality - Toba Dist., Samosir, Sumatra, INDONESIA.

Larva briefly described by Lenz 1937.

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Modified: 18 March 2019
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